1. Field of the Invention
The invention generally relates to insulating materials and, more particularly, to an insulating material which demonstrates improved resistance to heat conduction especially at lower temperatures within a liquid environment as well as exhibiting selected desirable heat conduction characteristics in a gaseous (e.g. air) environment. More particularly, the present invention also relates, for example, to a scuba wet suit or other articles of clothing which are made from this insulating material and which, when incorporated into the clothing, demonstrates improved buoyancy properties over a wide range of ambient pressure.
2. Description of the Related Art
At the present time, many recreational and occupational activities are carried out in environments which can differ greatly from conditions that would be considered xe2x80x9cnormalxe2x80x9d for most humans and garments and other equipment specific to various activities are known for enhancement of comfort and safety. While a degree of comfort is considered desirable for recreational activities, some provisions are often made to enhance safety. In occupational activities, comfort may be secondary to safety but some enhancements for comfort are generally provided. In practice, however, there is little distinction made between provisions for safety and comfort other than a a matter of severity or varibility of conditions which can be made tolerable and equipment having such provisions are collectively referred to as xe2x80x9cprotectivexe2x80x9d.
Nevertheless, provisions made for some conditions may not be fully successful and may, in fact, engender some additional safety considerations. Consider, for example, an underwater environment (for either a recreational or occupational activity). It is well-recognized that water will remove heat from (or transfer heat to) a surface about twenty times more rapidly than a gaseous environment at the same temperature due to, among other considerations, enhanced convection effects and greater specific heat. Therefore, a liquid environment may not be comfortable even at temperatures that would be comfortable in air and increased temperature differences may become debilitatingly uncomfortable or dangerous. Moreover, water will usually be somewhat colder than the air above the surface due to evaporative cooling and other effects and temperature will generally decrease with increasing depth. Accordingly, most protective garments adapted for an underwater environment will usually include materials having some insulative qualities even though the materials may have uncomfortable or potentially dangerous qualities above the liquid/water surface.
In the case of a so-called wet suit which has become familiar for use with self-contained underwater breathing apparatus (SCUBAxe2x80x94often used to refer to the suits themselves) a relatively tight-fitting generally waterproof resilient material is used to reduce convection effects in liquid within the wet suit close to the body of the wearer while the waterproof material (generally low density neoprene or the like) is formed with air spaces therein to decrease heat loss through the material. The tight fit and the surface qualities of the material make the wet suit difficult and uncomfortable to put on and, more importantly, in the atmosphere, substantially prevents evaporation of perspiration from the body; a primary temperature regulating mechanism of the human body. Accordingly, aside from the increased discomfort of the wet suit, in general, the human body in a wet suit can easily and quickly become dangerously overheated when in a gaseous rather than liquid environment. (Although the effect may be relatively small, an instability of thermal regulation may also be present since increased temperature of the wet suit material from body heat as well as radiant energy (e.g. sunlight) heating may expand the air spaces and increase the insulative characteristics thereof.) Accidental heat stroke while wearing a wet suit is not uncommon.
The nature of conventional insulation in a wet suit also presents some additional safety concerns and potential dangers as well as presenting substantial costs and inconvenience in use. Specifically, the air spaces formed in the material of the wet suit are compressible while liquids such as water have substantial mass/density and are substantially incompressible. The mass/density of water thereof causes pressure to increase rapidly with depth (e.g. about one atmosphere for each thirty-three feet or by a factor of about five at one hundred thirty feet, the maximum depth considered reasonably safe for recreational use of SCUBA gear). The effect of this increase in pressure is to compress and decrease the volume of air spaces in the wet suit material; decreasing the insulative qualities with increasing liquid depth where reduced liquid/water temperatures are more likely to be encountered. Therefore, a wet suit is very limited, as a function of depth, to provide suitable insulating qualities and comfort for the wearer.
Much more importantly, however, the compressibility of the air spaces in wet suit material cause a significant instability in buoyancy. If a wet suit were to be fabricated which included a total air space volume for neutral buoyancy of a wearer at a depth of, for example, thirty feet, positive buoyancy would be developed at shallower depths while negative buoyancy would be developed at greater depths. Since positive buoyancy causes a tendency to float while negative buoyancy causes a tendency to sink and the change in buoyancy is a function of water pressure and depth, these effects become more pronounced with increased excursion from the neutral buoyancy depth. Moreover, thicker wet suits intended to provide greater insulation for use at greater depths increase the severity of this instability in buoyancy while being less flexible and more limiting of body motion.
In order to counteract this instability in buoyancy, buoyancy correction devices (BCD) are known for prevention of uncontrolled ascent or descent. As a diver descends to greater water depths, the diver may increase inflation of the BCD to counteract loss of buoyancy of the wet suit but must bleed air from the BCD during ascents. However, small errors in control of a BCD by a diver can and often do result in uncontrolled ascents or descents; from which serious injury or even death can result.
Further, in order to limit the severity of changes in buoyancy, a wet suit might be fabricated to be neutrally buoyant at a projected average depth of use; resulting in positive buoyancy for a significant depth below the water surface. Since BCDs are principally intended to increase buoyancy to a substantially neutral level when the air spaces in the wet suit are significantly compressed, a diver must carry a significant amount of weight in order to be able to achieve sufficiently neutral buoyancy at the surface to descend underwater at all. In an emergency it may be necessary to jettison some or all of these weights during ascent. Therefore, the weights must be fabricated to be securely held on the body and yet be readily removable as may be required.
Such problems and safety concerns are not confined to wet suits but are common to other types of diving suits which may, in fact, present additional but related problems. For example, the so-called dry suit, like the wet suit, may also be made of a positively buoyant low-density neoprene which is subject to the same compression characteristics and instability of buoyancy but to a somewhat reduced degree since thinner material is used. The dry suit is not tight-fitting and allows additional insulating garments to be worn. Additional insulation is provided by air inside the dry suit and the additional insulating garments. However, the air within the dry suit is compressible and additional air must be added within the dry suit as depth increases to maintain insulation and resist water incursion into the dry suit which would further reduce the insulation properties of the additional insulating garments. This additional air must be vented during ascent to avoid excess buoyancy. (While BCDs are recommended for use with dry suits, many divers perform buoyancy compensation by adding air to and venting air from the dry suit alone.)
However, the total amount of air even in a fully vented dry suit generally exceeds the amount of air encapsulated in air spaces in a wet suit and the instability of buoyancy is relatively increased. Also, to attain sufficiently neutral buoancy at the water surface relatively more weights must be worn. Ankle weights are also often necessary and generally worn to avoid air within the dry suit moving to the legs thereof and holding the diver in an inverted position. Further, air cannot be vented from the dry suit in an inverted position and uncontrolled ascents are less avoidable or recoverable in such an event. Since the movement of air to the legs of a dry suit can be initiated from a number of positions of a diver, a substantial additional safety hazard is presented. Similar problems are present to some degree in virtually all known protective garments for underwater use.
In summary, known techniques for providing insulation with a flexible material have involved structures which present an unavoidable instability of buoyancy (as well as some temperature-related hazards when not immersed in liquid) while not being fully successful in limiting heat loss over a range of water depths. Even under circumstances where the insulating material is not immersed to substantial depths and instability of buoyancy is of little or limited importance, the reduction of air volume in most insulating materials radically reduces the insulative properties. For example, goose down and other fibrous and/or high loft materials that are known to be high-quality insulators under normal circumstances have little insulating quality when compressed or wet. Therefore, there has been no alternative to the above-described materials and their undesirable and potentially dangerous effects where submersion was contemplated or the potential loss of insulating properties of other materials under circumstances which may be unavoidable.
It is a first object of the present invention to provide an insulating material which demonstrates improved resistance to heat loss as temperature descends in a fluid environment.
It is a second object of the present invention to provide an insulating material which, when used in a fluid environment, exhibits improved buoyancy properties especially at increased pressures.
It is another object of the present invention to provide a wet suit made from an insulating material which satisfies the first and second objects, and which therefore keeps a wearer of the suit warmer at diving depths and allows the diver to achieve neutral buoyancy within a range of diving depths with our without using a buoyancy compensation device used by conventional wet suits.
It is another object of the present invention to provide a wet suit which is thinner than conventional wet suits, especially those made from neoprene or other elastic materials which rely on trapped air bubbles for positive buoyancy and which also rely on a buoyancy compensation device for neutral buoyancy at lower diving depths.
It is another object of the present invention to provide a wet suit which is looser fitting, more flexible, and easier to put on and take off than conventional wet suits.
It is another object of the present invention to provide a wet suit which is safer to use, especially by physically and/or mentally handicapped individuals.
It is another object of the present invention to provide an article of clothing made from an insulating material which demonstrates the aforementioned heat conduction properties and, for life-saving purposes, is biased with a positive buoyancy so that individuals wearing the clothing (fisherman, oil platform workers, pilots, surfers, water skiers and other sportsman, etc.) may stay afloat until help arrives.
These and other objects of the present invention are achieved by providing an article of insulation which includes at least one support layer and a plurality of containers supported by the at least one support layer. Each of the containers have rigid walls which enclose either a vacuum or a gas. When in water, the rigid-wall containers provide insulation and buoyancy which makes the insulation ideal for clothing and wet suits, described in the embodiments which follow. These properties may be enhanced by making the support layer from thermal insulation material and/or one which itself exhibits a desired buoyancy. To increase its suitability for clothing and wet suits, the support layer may be made from a flexible, elastic material. The containers may be formed as beads which are spherical or non-spherical in shape, or the containers may have a tubular shape. Further, the beads may all be of the same size or the sizes may be alternated to achieve a desired buoyancy and/or insulation profile.
In accordance with one embodiment, the containers are embedded with in a single support layer. In accordance with another embodiment, the support layers are attached to one another in a quilt pattern. In the quilt pattern, pockets are formed for holding one or more containers. The containers may be left to freely move within the pockets or an absorbent powder may be added which gels when exposed to water.
The present invention is also a wet suit made from the insulation material described above. The wet suit may be entirely made of this insulation material, or the insulation material may be formed on selected portions of the wet suit. The size, number, and arrangement of the containers may be selected to achieve desired buoyancy and insulation properties. For example, the suit may be designed to have positive buoyancy at the surface, or improved neutral buoyancy substantially throughout a wide range of diving depths.
The wet suit of the present invention is able to outperform conventional wet suits in a number of ways. First, the wet suit of the present invention demonstrates improved resistance to heat conduction compared with conventional wet suits. This results from the use of an insulating material with rigid-wall containers which do not compress with water depth. Second, the wet suit of the present invention demonstrates improved buoyancy properties compared with conventional wet suits, also as a result of using non-compressible, rigid-wall containers. Third, the wet suit of the present invention is safer to use than conventional wet suits because the buoyancy provided by the rigid-wall containers. The wet suit of the present invention is also more comfortable to wear than conventional suits.
The present invention is also an article of clothing made from the insulation material described above. This clothing may be in the form of jackets, pants, shirts, vests, and the like. The rigid-wall containers may be made to demonstrate a positive buoyancy, thereby turning the clothing into a safety device when its user falls into the water.